The embodiments described herein relate generally to electrical switchgear, and, more specifically, to an arc chute assembly for use in an automatic transfer switch (ATS) and methods of assembly thereof.
Transfer switches are used, for example, to quickly connect an emergency power source to a load when a normal power supply fails. For example, facilities such as hospitals, telecom or datacenters, and transportation systems use transfer switches to maintain continuous electrical power when a power failure occurs in the electrical utility service to the facility. When a utility power failure occurs, the transfer switch connects the facility to a backup power generator without significant interruption of electrical power to the facility. A user can either manually or automatically select among multiple sources of backup power to feed the maintained loads. There is a long felt need for mechanically simple and reliable transfer switches which effectively suppress electrical arcs.
Transfer switches and other electrical switching apparatuses typically include a set of stationary electrical contacts and a set of moveable electrical contacts. The stationary and moveable contacts are in physical contact with one another when it is desired that the circuit breaker provide electrical current to a load. However, when it becomes necessary to interrupt the circuit the moveable contacts are moved away from the stationary contacts, thus removing the moveable contacts from physical contact with the stationary contacts and creating a space therebetween. This may result in the formation of an electrical arc beginning at the time the contacts are separated.
In these particular instances, electrical arcs (also known as “arc discharges”) are undesirable for a number of reasons. First, they provide a pathway for current to flow through the circuit breaker to a load when it is desired that the load be isolated from such current. Additionally, the electrical arc extending between the contacts often results in vaporization or sublimation of the contact material itself, eventually resulting in destruction or pitting of contacts.
As a result, manufactures of switching gear use arc chute mechanisms to facilitate quenching of this undesirable arc discharge. However, at least some known arc chutes tend to degrade and breakdown dielectrically over time after many arcing events due to degradation of the insulated arc chute housing from the intense heat generated by the arc. As such, what is needed is an arc chute that maintains the integrity of the plastic arc chute housing and prevents contact degradation.